The invention relates to novel compounds which are used in the pharmaceutical industry as active compounds for the production of medicaments.
U.S. Pat. No. 4,468,400 describes tricylic imidazo[1,2-a]pyridines having various ring systems fused onto the imidazopyridine parent structure, which are said to be suitable for the treatment of peptic ulcer disorders.
The invention relates to compounds of the formula I 
in which
R1 is methyl or hydroxymethyl,
one of the substituents R2a and R2b is hydrogen and the other is hydroxy, methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
one of the substituents R3a and R3b is hydrogen and the other is hydroxy, methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
where R2a or R2b on the one hand and R3a or R3b on the other hand are not simultaneously hydroxy, and their salts.
Suitable salts of compounds of the formula I are especially all acid addition salts. Particular mention may be made of the pharmacologically tolerable salts of the inorganic and organic acids customarily used in pharmacy. Those suitable are water-soluble and water-insoluble acid addition salts with acids such as, for example, hydrochloric acid, hydrobromic acid, phosphoric acid, nitric acid, sulfuric acid, acetic acid, citric acid, D-gluconic acid, benzoic acid, 2-(4-hydroxybenzoyl)benzoic acid, butyric acid, sulfosalicylic acid, maleic acid, lauric acid, malic acid, fumaric acid, succinic acid, oxalic acid, tartaric acid, enbonic acid, stearic acid, toluenesulfonic acid, methanesulfonic acid or 3-hydroxy-2-naphthoic acid, where the acids are employed in salt preparationxe2x80x94depending on whether a mono- or polybasic acid is concerned and depending on which salt is desiredxe2x80x94in an equimolar quantitative ratio or one differing therefrom.
Pharmacologically intolerable salts which can be initially obtained as process products, for example in the preparation of the compounds according to the invention on an industrial scale, are converted into pharmacologically tolerable salts by processes known to the person skilled in the art.
According to expert""s knowledge the compounds of the invention as well as their salts may contain, e.g. when isolated in crystalline form, varying amounts of solvents. Included within the scope of the invention are therefore all solvates and in particular all hydrates of the compounds of formula I as well as all solvates and in particular all hydrates of the salts of the compounds of formula I.
The compounds of the formula I have three chiral centers. The invention relates to all eight conceivable stereoisomers in any desired mixing ratio with one another, including the pure enantiomers, which are a preferred subject of the invention.
A preferred embodiment of the invention are compounds of the formula I* 
in which
R1 is methyl or hydroxymethyl,
one of the substituents R2a and R2b is hydrogen and the other is hydroxy, methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
one of the substituents R3a and R3b is hydrogen and the other is hydroxy, methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
where R2a or R2b on the other hand and R3a or R3b on the other hand are not simultaneously hydroxy, and their salts.
An embodiment (embodiment a) of the invention are compounds of the formula I*, in which
R1 is methyl,
one of the substituents R2a and R2b is hydrogen and the other is methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
one of the substituents R3a and R3b is hydrogen and the other is hydroxy,
and their salts.
A further embodiment (embodiment b) of the invention are compounds of the formula I*, in which
R1 is methyl,
one of the substituents R2a and R2b is hydrogen and the other is hydroxy,
one of the substituents R3a and R3b is hydrogen and the other is methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
and their salts.
A further embodiment (embodiment c) of the invention are compounds of the formula I*, in which
R1 is methyl,
one of the substituents R2a and R2b is hydrogen and the other is methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
one of the substituents R3a and R3b is hydrogen and the other is methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
and their salts.
A further embodiment (embodiment d) of the invention are compounds or the formula I*, in which
R1 is hydroxymethyl,
one of the substituents R2a and R2b is hydrogen and the other is methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
one of the substituents R3a and R3b is hydrogen and the other is hydroxy,
and their salts.
A further embodiment (embodiment e) of the invention are compounds of the formula I*, in which
R1 is hydroxymethyl,
one of the substituents R2a and R2b is hydrogen and the other is hydroxy,
one of the substituents R3a and R3b is hydrogen and the other is methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
and their salts.
A further embodiment (embodiment f) of the invention are compounds of the formula I*, in which
R1 is hydroxymethyl,
one of the substituents R2a and R2b is hydrogen and the other is methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
one of the substituents R3a and R3b is hydrogen and the other is methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
and their salts.
Preferred compounds of the embodiments a to f are those, in which R3b is hydrogen.
Particularly preferred compounds of the embodiments a to f are those, in which R2a and R3b are hydrogen.
Preferred compounds within the scope of the invention are those of embodiment a, which can be characterized by the formula I** 
in which
one of the substituents Ra and Rb is hydrogen and the other is methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy
and their salts.
Particularly preferred compounds of embodiment a are these of formula I**, in which
Ra is hydrogen and
Rb is methoxy, ethoxy, isopropoxy, methoxyethoxy or methoxypropoxy,
an their salts.
With the aid of the general formula I*, the following exemplary preferred compounds according to the invention may actually be mentioned by means of the substituent meanings for R1, R2a, R2b, R3a and R3b in the following Table 1 (Tab. 1):
The compounds according to the invention can be prepared as described by way of example in the following examples, or using analogous process steps starting from appropriate starting compounds (see, for example, EP-A-0 299 478 or Kaminski et al., J. Med. Chem, 1985, 28, 876892). The starting compounds are known or can be prepared analogously to the known compounds The compounds according to the invention can be prepared for example starting from N-protected 8-amino-imidazo[1,2-a]pyridines according to the following reaction scheme: 
The above scheme represents an example of an enantioselective synthesis. The N-protected (Piv represents a customary protective group, preferably the pivaloyl group), 8-aminolmidazo[1,2-a]pyridine, deprotonated in the 7-position is reacted with an enantiomerically pure dioxolane. This initially leads to a condensation product which can be cyclized under strongly acidic conditions with removal of the protecting groups. The subsequent reduction of the keto group using sodium borohydride leads in over 90% enantiomeric purity to the 7,8-trans-diol indicated. The subsequent etherification which is carried out according to known processes, e.g. as described in the Examples, leads to the final products of formula I* in which R2a and R3b are hydrogen. The corresponding 7,8-cis-compound is obtained from the mother liquor, which is left after separating off the 7,8-trans-compound, by chromatographic purification.
The substances according to the invention are isolated and purified in a manner known per se, for example, by distilling off the solvent in vacuo and recrystallizing the residuo obtained from a suitable solvent or subjecting it to one of the customary purification methods; such as, for example, column chromatography on suitable support material.
Salts are obtained by dissolving the free compound in a suitable solvent, e.g. In a chloronated hydrocarbon, such as dichloromethane or chloroform, or a low molecular weight aliphatic alcohol (ethanol, isupropanol) which contains the desired acid, or to which the desired acid is subsequently added. The salts are obtained by filtering, reprecipitating, precipitating with a nonsolvent for the addition salt or by evaporating the solvent. Salts obtained can be converted by alkalization or by acidification into the free compounds, which in turn can be converted into salts. In this way, pharmacologically intolerable salts can be converted into pharmacologically tolerable salts.
The pure enantiomers, in particular the pure enantiomers of the formula I*, to which the invention preferably relates, can be obtained in a manner familiar to the person skilled in the art, for example by enantioselective synthesis (see, for example, the Scheme), by chromatographic separation on chiral separating columns, by derivatization with chiral auxiliary reagents, subsequent separation of diastereomers and removal of the chiral auxiliary group, by salt formation with chiral acids, subsequent separation of the salts and liberation of the desired compound from the salt, or by (fractional) crystallization from a suitable solvent. Trans-products obtained (with R2a and R3b=hydrogen) can be converted (at least partly) to the corresponding cis-products (with R2b and R3b=hydrogen) by standing under acidic conditions (e.g. 2 equivalents of acid, such as sulfuric acid) in the corresponding alcohol R2xe2x80x94OH. Likewise, cis-products obtained can be converted to the corresponding trans-products. The cis- and trans-products are separated e.g. by chromatography or by crystallization.
The following examples serve to illustrate the invention further without restricting it. Likewise, further compounds of the formula I whose preparation is not described explicitly can be prepared analogously or in a manner familiar to the person skilled in the art using customary process techniques. The abbreviation min stands for minute(s), h for hour(s) and ee for enantiomeric excess.